This proposal describes a 5 year training program for the development of an academic career in Neonatology. The principle investigator is an Assistant Professor in the Department of Pediatrics at Baylor College of Medicine who is board certified in General Pediatrics and Neonatal/Perinatal Medicine. She completed a Pediatric residency at Tufts University School of Medicine and a fellowship in Neonatology at Yale University School of Medicine. During her fellowship, the applicant developed a strong interest in cardiovascular development. This program will provide the applicant with an excellent research environment and protected research time to further develop scientifically towards becoming an independent investigator. She will be mentored by Dr. Karen Hirschi, a recognized expert in the field of vascular biology with a strong record of mentoring graduate students and postdoctoral fellows. The proposed studies include a collaboration with Dr. Mary Dickinson at the Beckman Institute at Caltech, who is pioneering advanced imaging strategies to study early stages of mouse embryonic development. An advisory committee of well established scientists and clinician scientists will provide additional scientific and career guidance. The research proposal focuses on the cellular and molecular regulation of vascular remodeling during embryonic development. Recent data from the Hirschi laboratory have demonstrated that defects in yolk sac remodeling can result from dysregulation of cell cycle control and lack of secreted growth factors from the yolk sac visceral endoderm. This proposal will examine the contribution of cell migration to the process of vascular remodeling. The specific aims include: 1) Defining the stage-specific role of endothelial cell migration during murine yolk sac vascular development in vivo, 2) Determining which specific visceral endodermal-derived factor(s) regulates endothelial cell migration during vascular remodeling, and 3) Identifying the intracellular signaling pathways that mediate endothelial cell migration during the process of vascular remodeling.